Electronic devices, such as integrated circuits and flat panel displays, are commonly fabricated by a series of process steps in which layers are deposited on a substrate and the deposited layers are etched into desired patterns. In some instances, the process steps include plasma enhanced chemical vapor deposition (PECVD) processes. The trend in microelectronic circuits toward ever increasing densities and smaller feature sizes continues to make plasma processing of such devices more difficult. For example, in single wafer systems, pressure differences and differences in treatment gas concentration leads to non-uniformities across a surface of a wafer substrate, from a center of the wafer substrate to an edge of the wafer substrate. The non-uniformities become more pronounced as a diameter of the wafer substrate increases. Such non-uniformities cause a variety of problems. For example, in the manufacture of semiconductors and integrated circuits, such non-uniformities often result in devices that either do not function or function in a decreased capacity.
Previous techniques utilized different gas distribution plates or focus rings for substrates having different diameters in order to compensate for non-uniformities of the treatment gas. Identifying and installing the correct gas distribution plate or focus ring is time consuming and costly. In addition, the appropriate gas distribution plate for a particular process is often not suitable for a different process. Consequently, in order to use the same chamber for different processes, the gas distribution plate is replaced which decreases an amount of time the chamber is operating, thereby reducing a production yield. In addition, in gas distribution plates which provide concentric control of treatment gas flow, the non-uniformity of the wafer surface is increased.